Wind vanes, also referred to as weather vanes, are generally configured to determine the direction of the wind. In general, most, if not all, types of wind vanes share common components and operate in a similar manner when determining wind direction. For example, a wind vane may include a rotating portion and a stationary portion. The rotating portion may include a head coupled to a tail and the stationary portion may include a base, wherein the head and tail are configured to rotate about a vertical axis of rotation in relation to the base (i.e. in a direction parallel to a plane perpendicular to the axis of rotation). The wind vane may be configured to align with the wind aerodynamically. In particular, the rotating portion is configured to move (e.g., rotate) in response to a change in wind direction. A difference in angular position between the stationary portion and the rotating portion generally corresponds to a wind direction.
Wind vanes may be used in a variety of applications. For example, in the wind energy industry, wind wanes may be included in wind turbine control systems. These types of wind vanes may be referred to as turbine control vanes. Wind turbines are generally used in high wind areas and may be subject to strong winds which may change direction from moment to moment. To enable wind turbines to consistently receive the maximum force of wind, movement of a wind turbine may be controlled by a turbine control system, wherein the control system positions the wind turbine, specifically the rotational axis of the wind turbine, to be aligned with the wind vector. The turbine control system takes into account various wind parameters, such as, for example, wind speed and wind direction, when determining the most efficient (i.e. maximum energy extraction) position of the turbine. As such, turbine control systems may include one or more turbine control vanes for the indication of wind direction in order to determine proper positioning of wind turbines.
A common characteristic of wind vanes, including turbine control vanes, is that the rotating portion may oscillate several times about the vertical axis when wind direction changes before pointing into the wind again. Furthermore, turbulence may cause the rotating portion to be positioned off-line relative to the wind vector and remain thus misaligned for a period of time. For example, during operation, a turbine control vane may be disturbed by, for example, a wind gust, sudden change of wind direction, and the like which may cause the turbine control vane to swing uncontrollably. For example, a turbine control vane may be positioned on a wind turbine and may be operating in the wake of the wind turbine rotor. As such, the turbine control vane may be subjected to turbulence with wind speed and direction that may change significantly and quickly. As a result, the turbine control vane may swing wildly and may rotate a full revolution at times. A turbine control system coupled to and communicating with the turbine control vane may be relying on directional data from the turbine control vane in order to determine proper positioning of the wind turbine.
In the event that the turbine control vane is rotating uncontrollably, the vane may present output errors to the turbine control system beyond certain tolerances. In particular, when the control system receives directional data indicating that the vane is swinging uncontrollably, the control system may be configured to shut down the wind turbine as a safety measure. More specifically, uncontrolled swinging of the turbine control vane may indicate strong off-axis winds that may damage the wind turbine if the wind turbine is allowed to continue operating in the current position. Additionally, uncontrolled rotation of the vane may result in increased wear thereby reducing the life of the vane.
As such, some wind vanes, including turbine control vanes, may include damping means to accommodate for any sudden disturbances, such as, for example, wind gusts, sudden changes in wind direction, etc. However, current damping means have several drawbacks. For example, some wind vanes may be under damped (i.e., less than critically damped), particularly in high winds, resulting in poorly damped oscillation after being disturbed by, for example, a wind gust, sudden change of wind direction, turbulence of the turbine rotor, and the like. Additionally, some damping means may cause a wind vane to be inaccurate or unresponsive in low wind conditions. Additionally, some damping methods may reduce the effectiveness of heating systems incorporated into the wind vane and intended to keep the vane, as well as the wind turbine, operational in icing conditions.